9

1100 Chapter 9: Surface Modeling
• An easy way to animate a growing surface is to
put a curve point (page 1–1220) with t rimming
onacurve,thenanimatetheUpositionofthe
curvepoint,andthenusethiscurveastherail
of a 1-rail sweep (page 1–1204). As the trimmed
rail grows, so does the sweep surface. (You
must trim the curve before you create the sweep
surface.)
• If you see gaps between surfaces in rendered
images, increase the value of Merge for the
renderer in the surface approximation (page
1–1239) sett ings.
• If a texture slides around on the surface during
animation, t his i s because you are using the
default Chord-Length parameterization of the
texture surface. Select the surface, then on
the Material Properties rollout (page 1–1149)
change the parameterization to User Defined.
Now the texture should stick to the surface
better.
•Don’tusetheUV W Map modifier (page 1–922)
to apply a texture to an animated NURBS
surface.
• If a surface seems to glitter or jump around
as you move toward it in an animation, this
is because View Dependent tessellation is on
(on the Surface Approximation rollout (page
1–1239)) so the tessellation is constantly
changing. Usually View Dependent creates no
visible changes, but if it does, tur n it off.
• If a surface seems to glitter or jump around
while it changes during animation, this
is because the tessellation is changing as
the surface animates. Changing surface
approximation (on the Surface Approximation
rollout) to Regular fixes this in all cases.
Parametric tessellation also solves this problem
for every kind of surface except Ulofts(page
1–1196) and U V lofts (page 1–1200).
• If the View Dependent setting doesn’t seem
to be doing much, change the tessellation
(ontheSurfaceApproximationrollout)from
Curvature to Spatial. You will then get a much
more drastic change in face count.
•Togetamaptosmoothlycovertwoormore
surface without tiling, create another surface
whose shape cov ers and roughly conforms to
the original surfaces. Apply the texture to the
larger sur face. In the Material Properties rollout
(page 1–1149) for the original surfaces, set
Texture Surface to Projected, click Pick Source
Surface, and pick the larger surface. Adjust the
larger surface to fine-tune the map projection.
Hide the larger surface before you render.
• To have different maps on a surface sub-object,
use different mapping coordinates (page 3–967),
and multiple map channels (page 3–966).On
the Material Properties rollout (page 1–1149),
change the Map Channel value and then turn
on Generate Mapping Coordinates. (Each
map channel requires its own set of mapping
coordinates.)
NURBS surface sub-objects let you set the map
channel d irectly, and don’t require you to apply
UVWMapmodifiersasotherobjectsdo.
•Ifamapdoesn’taligntoasurfacesub-objectthe
way you want it to, on the Material Properties
rollout (page 1–1149) choose User Defined as
the Texture Surface, and then use Edit Texture
Points or the Edit Texture Surface dialog to
movethepointsofthetexturesurface.
• To adjust how the map aligns to the edges of
a surface sub-object, use the Texture Corner
settings on t he Material Properties rollout (page
1–1149).